Slow, fast, short trips, whatever my truck is overheating. I started off with a quick look over and there was no thermostat installed. Will this fix the problem? There is also a crack around the radiator inlet on the drivers side and there is no overflow installed. The truck is a 1985 K5 Blazer with a 305. I have a 160* thermostat I am going to put in before work today. I might take it to work to see if it overheats again. Besides the cracked radiator there are no known leaks. The water pump indeed pumps and I noticed early on it was really low on coolant so I topped it off and have done my best to get all possible bubbles out. Any ideas?